The researchers stress that the study does not show that the highly processed foods caused the cancers. People who eat a lot of junk food have other habits that predispose them to cancer, not the least of which is smoking.

We are a long way from understanding the full implications of food processing for health and wellbeing

But they took into account many of these, including smoking but also age, sex, educational level, family history of cancer, and physical activity — and they still found the link between eating junk food and cancer.

There are several ways that processed foods could in theory raise cancer risks, they noted.

“Firstly, ultra-processed foods often have a higher content of total fat, saturated fat, and added sugar and salt, along with a lower fiber and vitamin density,” they said.

Related

“Finally, ultra-processed foods contain authorized, but controversial, food additives such as sodium nitrite in processed meat or titanium dioxide (TiO2 , white food pigment), for which carcinogenicity has been suggested in animal or cellular models,” they added.

Other researchers pointed out that ultra-processed foods is both a broad and vague category.

“Results from this study support the claim that the shift in the world’s food supply to highly processed foods may partly account for increasing trends in the incidence of non-communicable diseases, including cancer,” Martin Lajous and Adriana Monge of the National Institute of Public Health in Mexico wrote in a commentary.

“We are a long way from understanding the full implications of food processing for health and well-being,” they added.